Mechanotransduction in Breast and Ovarian Cancers: Using Bioreactors to Study the Cellular Response to Physiological Mechanical Stimuli

Abstract

Cells within the body experience a wide range of dynamic mechanical stimuli. These stimuli are exacerbated in cancers and can alter the progression of the disease. As the tumor grows and expands, it presses out against the surrounding matrix and cell environment, creating internal compressive forces. The growing tumor also alters interstitial and vascular blood flow thereby enhancing shear stress exposure. How cells translate this mechano-environment into downstream signaling is known as mechanotransduction. Though preliminary research has touched on the influence physiological mechanical stimulus can have on cancer progression, the work remains erratic on cell metastasis, gene expression, proliferation, and chemotherapeutic response. In order to address this unknown effect on cellular phenotypes and treatment response, two bioreactors capable of tunable three-dimensional stimulus with either shear stress or compressive stress were developed. Breast and ovarian cancer cells were first encapsulated within a 3D combination agarose/collagen-I hydrogel and then exposed to physiological mechanical stimuli relevant to the unique microenvironments of pleural effusions and ascitic environment respectively for 24 to 72 hours. Stimulated cells were then assessed for morphological alterations, altered gene expression (RT-qPCR), proliferation (ki67 expression), and drug resistance via standard chemotherapeutic treatment (cell death via casp-3 expression). Breast cancer cells exposed to varying levels of shear stimulus occurring within the pleural effusion microenvironment showed stimulus aided in cancer cell proliferation, invasive potential, and survival in the presence of paclitaxel treatment concurrent with the activation of the PLAU and COX2 pathways. Next, ovarian cancer cells were subjected to compressive forces found within the solid tumor microenvironment and as consequence of the hydrostatic pressure caused via ascitic fluid retainment. Ovarian cancer proliferation, morphological elongation, and enhanced survival was observed under physiological compressive stimulus alongside chemoresistance and upregulation and activation of CDC42. Finally, ovarian cancer cells were stimulated with shear stresses representative of ascitic fluid buildup in the peritoneal cavity in ovarian cancer patients. This shear stress conditioning altered cellular morphology, enhanced proliferation as well as chemoresistance to dual chemotherapeutic drug treatment with paclitaxel and carboplatin. This alteration in cellular phenotype was found alongside consistent downregulation of MUC15, a potential protein of interest for future mechanotransduction studies. Overall, findings suggest that this dynamic mechanical environment aids in the advancement of cancer migration, proliferation, and chemoresistance which may be mitigated by targeting various mechanotransduction pathways. This is the first reported tie of shear stress stimulation to PLAU and COX2 pathway activation in breast cancer. Additionally, this is the first time mechanotransduction has been tied to CDC42 activation and MUC15 downregulation in ovarian cancer. The bioreactors constructed and utilized for this study provide 3D platforms ideal for understanding the influence of compressive and shear stress stimulus on cellular behavior, a critical component to our understanding and improvement of cancer patient treatments.